Biological index and pollution assessment of Damghanroud river in the Semnan province

Fresh Water Rivers are one of the most important aquatic ecosystems in arid and semi-arid regions of Iran in point of biodiversity and drinking water views. Damghanroud River is one of these rivers at Semnan province that during past years has been threatened by drought and anthropogenic pollutions. This river supplies some parts of drinking water of Damghan city and some vicinity villages. The aim of the present study is to consider Biological Index of the river; for this purpose, limnological and hydrobiological studies of the river were carried out. At this study, seven sampling stations were determined based on limnological standard method along the river; afterwards sampling of invertebrates (Biological Index) and water quality (BOD) were performed seasonally during study period. The results showed that the first station (Cheshmeh-Ali) is free of pollution while the fourth sampling station (Doab) is the most polluted region at the river because the first station has no pollutant resource but the fourth station directly receives wastewater of agricultural activities and rural wastewaters. According to biomonitoring and water BOD measurement findings, Damghanroud River has relatively polluted situation and is classified in β-mezosaprobe class and benthos biological index has been deteriorated at this river.